DEPARTMENT OF BOTANICAL RESEARCH. 91 



territory corresponding roughly to but somewhat less than the eremaic 

 and arid regions, the mean annual temperature is 65° to 75° F. 



In the far north the yearly evaporation is 100 inches or more. In 

 the arid southwestern portion (Eucla) it is 95.98 inches. At Adelaide, 

 annual rainfall 20.95 inches, the yearly evaporation is 54.9 inches. 



The perennial vegetation of the drier portions of South Australia is 

 thus subject to high temperatures for a portion of the year, high 

 evaporation rates, a large number of days each year which are rainless, 

 and a relatively or actually low rainfall. In addition to these may be 

 mentioned intense insolation concerning which there are no available 

 data. Particular adjustments to the environment of the flora as a 

 whole and in certain details may be given in part as follows: In the 

 desert regions trees are confined to the water-courses, except such as 

 occur in the sandhills. In either case they are relatively small. Shrubs 

 are not numerous away from the water-courses, although they occur 

 sparingly in relatively dry situations on the high plains. On areas 

 which in the eremaic and arid regions are extensive, and where the 

 surface drainage is poor or wanting, halophytic shrubs are numerous 

 both Rs to species and individuals. It is probable, however, that in the 

 desert regions perennials in any situation are not sufficiently numerous 

 to prevent erosion by water or by wind. 



In the arid and subarid regions the trees and shrubs stray away 

 from the water-courses, so that in places open forests, as to trees, or 

 open pigmy forests, as to shrubs, are formed. The number of species 

 as well as of individuals is also greater. There is also a striking increase 

 in the transpiring surface of perennials. While such vegetational 

 features are closely related to the amount of the yearly rainfall, this 

 is not invariably the case. For example, in the southwestern portion 

 of the state, Ooldea, there is an extensive region of sandhills where the 

 annual precipitation is less than 10 inches, but where it is so well con- 

 served that the vegetation is more abundant than might be expected 

 from the amount of precipitation. 



The characteristic trees of the desert region (Oodnadatta) are 

 mainly Eucalyptus spp. and Acacia spp. Species of Eremophila are the 

 most striking shrubs of this region. 



In the arid region (Copley, Tarcoola, Ooldea, Port Augusta) the 

 number of trees and shrubs is very considerable and includes among 

 others the following genera: Acacia, Callitris, Cassia, Casuarina, Do- 

 doncea, Eucalyptus, Fusanus, Gravillea, Hakea, Heterodendron, Lepto- 

 spermum, Melaleuca, Myoporum, Petalostylis, and Zygophyllum. 



In the subarid regions (Quorn, Blanchtown, etc.) the number of 

 species of trees and shrubs is very considerable and need not be men- 

 tioned further. 



The halophytic vegetation is a characteristic feature of the arid and 

 desert regions. More than 50 species occur in the region east of Lake 



